High temperature mechanical properties of polycrystalline Y₂SiO₅

The high temperature mechanical properties of polycrystalline Y₂SiO₅ were studied in compression at temperatures in the range of 1200–1400 °C, both in constant strain rate and constant stress experiments. To examine the effect of grain size on the plastic deformation, two routes were used for the synthesis and sintering of Y₂SiO₅: one of solid state reaction followed by conventional sintering in air, and one of sol–gel synthesis followed by spark-plasma sintering, resulting in starting grain sizes of 2.2 and 0.9 μm, respectively. Ceramics obtained by these routes exhibited different high-temperature compression behavior: while the conventionally processed ceramic exhibited grain growth during mechanical testing and a stress exponent close to one, compatible with diffusional creep, the spark-plasma sintered ceramic showed no grain growth but significant cavitation, a stress exponent close to two and partially superplastic behavior. These results have implications for the design and lifetime assessment of rare earth silicate-based environmental barrier coatings.